1. Technical Field
The present apparatus and method relate to the tipping of surgical sutures with tipping agent to stiffen a portion of the suture prior to cutting.
2. Background of the Art
Tipping of surgical sutures is known in the art and is generally performed to prevent the brooming of a multifilament surgical suture when cut so that it may be more easily inserted into the shank end of a surgical needle.
For many years, surgeons have employed needle suture combinations in which a suture or ligature is attached to the shank end of a needle. Such needle suture combinations are provided for a wide variety of monofilament and braided suture materials, both absorbable and non-absorbable, e.g., catgut, silk, nylon, polyester, polypropylene, linen, cotton, and absorbable synthetic materials such as polymers and copolymers of glycolic and lactic acid.
One typical method for securing a suture to a needle involves providing a cylindrical recess in the shank end of a needle and securing a suture therein. For example, U.S. Pat. No. 1,558,037 teaches the addition of a cement material to such a substantially cylindrical recess to secure the suture therein. Additional methods for bonding a suture within a needle bore are described in U.S. Pat. Nos. 2,928,395 (adhesives) and 3,394,704 (bonding agents). Alternatively, a suture may be secured within an axial bore in a needle by swaging the needle in the region of the recess. See, e.g., U.S. Pat. No. 1,250,114.
Insertion of sutures into a hole, recess or tube for attachment to surgical needles presents problems peculiar to suture needle combinations. Braided multifilament sutures in particular are difficult to insert into the very small aperture of a surgical needle; unless modified, they are too limp for the suture tip to be controlled for insertion and they have a tendency to "broom", i.e, the filaments have a tendency to flare out at the cut end so that the diameter of the cut end exceeds the diameter of the needle hole. Various techniques have been employed to modify sutures to overcome the problems of limpness and brooming. One known method employs a tipping agent, which is a material used to coat the suture to stiffen the filaments and adhere them together.
Typically, a suture to be tipped is first placed under tension to reduce slack so that the suture may be maintained in a predetermined position on a frame or rack or other suture holding device. Optionally, the tension may be such as to reduce the diameter of the suture. See Canadian Patent No. 1,009,532. The suture is then dipped into the tipping solution and allowed to dry while under tension. The sutures are then dried, such as by being warmed in a drying oven at about 225.degree. F. for about 10 minutes. After drying the sutures can be cut and released from tension. The process results in a tipped end on each side of a cut. Where tension has optionally been employed to reduce the suture diameter, release of said tension will allow the suture to expand to its original diameter except at the tipped end portion. This can facilitate insertion of the end into a needle.
Tipping agents may be dissolved in solvents to form dipping solutions. By way of example, Mariotte mixture is a dipping solution comprising nylon dissolved in isopropyl alcohol. Other polymers and solvents may also be used. Gould mixture is a dipping solution comprising nylon dissolved in methanol. At least one major manufacturer of surgical needles recommends use of Mariotte mixture or Gould mixture for tipping sutures. A multitude of other tipping agents, including polymers and solvents, have been proposed. For example McGregor U.S. Pat. No. 3,890,975 discloses coating the suture with a binding resin or adhesive. The composition may be any non-toxic adhesive composition, either organic, inorganic or a hybrid. Suitable organic materials are such natural products as starch, dextrin, asphalt, animal and vegetable proteins, natural rubber, shellac, semi-synthetic products such as cellulose nitrate and the other cellulosies, polyamides derived from dimer acids, castor-oil based polyurethanes; such well-known synthetic resins as vinyl-type addition polymers, both resins and elastomers; polyvinyl acetate, polyvinyl alcohol, acrylics, unsaturated polyesters, butadiene/acrylonitrile, butadiene/styrene, neoprene, butyl rubber, polyisobutylene; and polymers formed by condensation and other step-wise mechanisms, i.e., epoxies, polyurethanes, polysulfide rubbers, and the reaction products of formaldehyde with phenol, resorcinol, urea, and melamine. McGregor states that particularly preferred bonding compositions are epoxide resins and polyester resins.
Schmitt U.S. Pat. No. 3,736,646 discloses that it is known to tip braided sutures by dipping the end of the suture in a plastic such as a solution in isopropyl alcohol. Schmitt suggest that for absorbable sutures an absorbable tipping agent is desirable, and proposes that a copolymer of lactic and glycolic acid dissolved in a suitable organic solvent, such as xylene or toluene, be applied to tip the suture.
Nichols U.S. Pat. No. 2,734,506 discloses a dipping solution of polymers of methacrylic acid esters in an organic solvent such as toluene, xylene acetone, ethyl acetate, methylethyl ketone, or naphtha.
Shepherd et al. U.S. Pat. No. 3,849,185 discloses the use of an acrylic casing syrup as a tipping agent, the syrup being fully polymerized after being applied to the suture.
In addition, paraffin/hexane solution (10% paraffin has been used as a suture coating agent as well as Arrochem (TM), a nylon resin plus methanol composition manufactured by ArroChem, Inc. of 201 Westland Farm Road, Mt. Holly, N.C. 28120, and SILASTIC (TM) Medical Adhesive (a silicon elastomer composition manufactured by Dow Corning Co.)
An improved method of tipping sutures is disclosed and described in U.S. Pat. No. 5,269,808, which is herein incorporated by reference in its entirety. In this method cyanoacrylate monomer is used as the tipping agent. The suture portion to be tipped is passed through a mist of cyanoacrylate which has been generated by an ultrasonically powered nozzle. The cyanoacrylate hardens very rapidly after being absorbed into the braided suture and adheres the filaments so that the filaments will not broom when the tipped portion is cut. One of the advantages of this method is that the cyanoacrylate works very well on sutures which have previously been coated and/or filled with lubricants, and/or therapeutic agents and the like.
While the spray application of cyanoacrylate has been effective for tipping sutures there is yet a need to apply the cyanoacrylate or other tipping agent more efficiently. In particular, it would be desirable to minimize the length of suture tipped so that little, if any, of the tipped portion extends out of the needle shank after needle-suture attachment.